Hydraulic pump



T. C. POULTER HYDRAULIC PUMP Nov. 9, 1943.

s sheets-sheet z Nav. 9, 1943. I T, c, PQULTER 2,333,885

Nov.` 9, 1943. T. c. POULTIFRy HYDRAULIC PUMP Filed July 2s, `194:.

5 Sheets-Sheet 4 DIRECT HYD ULIC 2800 EGO,

ISOQ 800 SOO |09 0 400 600 IZOO |600 000 i400 3805 820D 6600 4600 HYMUTUR RPM.

Nov. 9, 1943. 'r` c. POULTER 2,333,885

HYDRAULIC YUM? Filed July 28, 1941 5 Sheets-Sheet 5 Trowa/J Patented Nov. 9, 1943 UNIT-ED STATES PATENT GFFICE HYDRAULIC PUMP Thomas C. Poulter, La Grange, Ill.

Application July 28, 1941, Serial No.y 404,332

(Cl. S-126) 10 Claims.

'I'he present invention relates'to hydraulic pumps of a type suitable for use in hydraulic transmission systems.

One object of the invention is to provide a novel hydraulic pump mechanism characterized particularly by its improved and simplified arrangement for volumetric control of its output.

A more specific object is to 'provide a gear type hydraulic pump embodying a novel and Simplied arrangement for by-passing a selected portion of its output back to its inlet side, whereby to control the volumetric delivery rate of the pump.

Another object is to provide a hydraulic pump, embodying means for controllably varying its volumetric output, which pump is characterized particularly by its compactness, low Weight and all-over simplicity of construction.

Still another object is to provide a pump of the class indicated embodying a differential type set of impeller gears with each of a plurality of the intermediate or planetary gears arranged to utilize both of the groups of teeth on it (sepa.- rated by the diametrically opposed points of mesh of the same with the terminal gears) for pumping action, together with a novel arrangement for varying the volumetric output through the medium of a plurality of control devices, one for each planetary gear and each of which is adapted to control the output from both of said groups of teeth on the planetary gear with which itis associated.

Further objects and advantages of the inven tion will become apparent as the following description proceeds taken in connection with the Aaccompanying drawings in which:

sectional view of the pump Fig. 5 is a fragmentary face view of one 0f the wear plates included in the pump unit.

Fig. 6 is a detailed perspective view of the other of the wear plates included in the pump unit.

Fig. 7 is an enlarged' fragmentary detailed view showing the relation of the intake ports to the members of the pump unit.

Fig. 8 shows the torque-speed curve of the system. as well as the torque-speed curves for a conventional gear type transmission of comparable capacity.

fai

Fig. 9 is a schematic view of the system of Fig. 1 with a portion of the pump shown in developed form.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will describe in detail the preferred embodiment, but it is t0 be understood that I do not thereby intend to limit the invention to the vspecific form disclosed, but intend to cover all modifications andalternative constructions falling Within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to Fig. 1, I have shown therein an exemplary form of hydraulic transmission for an internal combustion engine I0 and which includes as an element thereof a hydraulic pump unit I I constructed in accordance with the present invention. This pump unit, which is driven by the engine, delivers pressure fluid, such as oil, to a suitable uid motor unit I2 of any desired form, connected to some driven member, indicated simply as a shaft I3 but which may, of course, be the axle of a vehicle, the propeller shaft of an airplane or ship, or any other of a number of driven devices.

In its exemplary form the pump unit II (see Fig. 2) is of the planetary gear type, comprising as terminal gear elements a sun gear I4 and an internally toothed ring gear I5, and as intermediate gear elements a plurality of (here shown as fve) planets I6. The sun gear I4 is fast on a drive shaft I3* (see Fig. 3) and the ring gear I5 is freely revoluble. The planets I6 are rotatable about their individual axes, though non-rotatable bodily about the axis of the sun gear.

The planets I6 are j'ournaled for rotation (see Fig. 3) about their individual axes on pins or stub shafts I1*l mountedl between a pair of stationary wear plates I 8, I9, which thus serve as the spider of the planetary gearing. The wear plate I9 is a simple at disk-shaped plate (see Fig.^5)

' scribed ports in the two plates.

members for the unit, shown in the form of end shields 2B and 2B (see Fig. 3). These end shields are metal castings, cored out to denne linternal passages corresponding with thehereinafter de- Thus the end shield 2l has a generally conical central portion 21 bordered at its periphery by an annular flange -portion overlying the corresponding portion of the outer face of the wear plate Il, and terminating at its center in a tapped inlet opening 28 in which is threaded a fluid supply conduit 36. The interior'of this end shield 2B is cored out to form an annular intake passage ll communicating with the opening 28 through a plurality of oblique interconnecting passages Il and encircling a central sleeve portion I2 in which the end of the drive shaft il'l is received.

.The other end shield 2l comprises a central sleeve portion 33, in which the drive shaft Il* is received and encircled by an annular outlet or exhaust passage ",leading to a tapped outlet opening 35 in which is threaded the end of a discharge conduit 29.

sandwiched between the wear plate Il and the end shield 28 is a valve block Il (Fig. 3) comprising a generally disk shaped forging or casting which is encircled by integral annular flanges 5| and B2. These ilanges are bolted respectively to the abutting end shield 26, by bolts I3. and tov which pass through registering holes in the other end shield 2 1, the wear plates IB and I9, and holes 24 in the retaining ring 2l. The stationary' parts of the pump are thus rigidly bolted together as a unitary structure, thereby making its installation at any particular point of use a comparatively simple matter.

In the valve block 50 are three bores 5B and two bores 5B, one for each of the planets VIl and axially alined with respective ones of them (see Figs. 3 and 4 and development in Fig. 9). yThe opposite ends of the bores l! comprise enlarged counterbores 58 and t1 while the inner ends of the -bores l5* are counterbored to a somewhat greater depth than the counterbores 50 by counterbores 56. The five bores 5B and l5* all communicate at their outer ends with the discharge chamber or passage 34 in the end shield 2l. The counterbores It and It, at the inner ends of the respective bores 5I and il* constitute, in effect, intermediate iiuid-receiving chambers into which the iluid is dischargedfrom the pump elements and from which it is, under the control of valve mechanisms described below, either by-passed back to the inlet side of the pump or directed to the outlet chamber 34, all as hereinafter detailed.

All of the gear-type impeller elements for the pump, that is gears i4, il and i0, have helical teeth (see, for example, the sun gear Il in Fig. 3). 'I'he so-called sealing lines between the respective planets. i8 and the ring gear II extend V along lines directly across each gear face, that is,

sealing linebetween each of the planets i! and the sun gear Il at a point diametrically opposite the first-mentioned sealing line with the ring gear. In other words, the series or groups of teeth on opposite sides of each planet are sealed parallel to their axes and likewise at the point of 'tangency of their pitch circles. There-is a similar Figs. 5 and 6). One inlet port in each pair is associated with a series of teeth on the corresponding side of its planet and one discharge port in each pair is associated with thev series of teeth on the corresponding side'of its planet.

'I'he ports I1 and Il are of what may be termed a comet shape" (Figs. 5 and 6). In each case the tails of the comets extend toward and substantially to a radial line passing through the respective centers of the sun gear and associated planet. Upon reference to the larger scale showingv in Fig. 7 it will be seen that the inner end walls 31 of the ports 31 lie along a line which, when projected, passes through the centers of the sun and ring gears and of the associated planet. These port end walls 31'L are of a length equal to the height of the teeth and extend between the base circles for the teeth of the adjacent mating gears. The side walls of the tail portions of the comet shaped ports extend along the base circles of the adjacent portions of the gear teeth and finally merge generally tangentially into the arcuate wall of the main body of the port, which may be formed initially by drilling a round hole. The diameter .of such hole is so chosen that the total effective crosssectional area of the port is equal to the product of the height of one of the gear teeth and the width of the gear face. By effective cross-sectional area of the port I mean its unobstructed cross-sectional area, that is, the total area minus the area of the ends of such teeth as are visible through the port. By so proportioning the port area relative to the gear, the velocity ofthe pressure nuid in passing through the port and subsequently around ythe gears does not undergo any substantial change. This elimination of throttling tends to conserve energy and to make for high emciency. The other or discharge ports 38 are formed in substantially the same manner in an opposite wear plate I9.

Upon reference to Fig, 5 it will be observed that .the separator bosses 20 on the wear plate l'present arcuate side faces and these faces are dimensioned to have'ay close running fit with the peripheries of the planets which they embrace. These bosses are cross-channeled along their corner edges as indicated at ll to' form crossvcirculation es leading from the intake ports l1. and the bosses are similarly cross` channeled on their other corners as indicated at lli, to form cross-circulation channels for the outlet ports 3l in the other wear plate Il. In each case the cross channels stop shortl of the full length of the boss side face and are deadended at the end opposite their corresponding ports.

With the port and tooth layout described above it will be appreciated upon reference to Fig. '1 that as the planet I6 revolves counterclockwise, its teeth move out of mesh with the ring and sun gears, respectively, while they are moving across the corresponding upper and lower intake ports 31, shown. Moreover, they unmesh, beginning at the trailing ends of the teeth adjacent these ports, and the unmeshing operation of each successiv'e tooth is continued progressively acres the width of the gear. Accordingly, the interdental spaces in the planet i6 open up, one after another, like pairs of jaws opening to the intake spaces between the teeth and the bosses 2U, and

is finally expelled through the discharge ports 38 as the planet teeth come into mesh with the gear and ring gear respectively.v While passing the exhaust ports 38 the planet teeth again come into mesh with the sun and ring gear teeth progressively from end to end of the planet teeth so that the pressure fluid is progressively expelled from the interdental spaces into the ex haust ports which register with the trailing ends of the interdental spaces.

Considering the operation of the pump unit as a whole, iiuid enters from the supply conduit 36 into the intake chamber 3| through which it passes to the intake ports 31. The impeller or gear elements of the pump, driven by the shaft I3", thereupon expel the pressure uid through the discharge ports 38 through'which it passes into the intermediate chambers defined by the colmterbores 55 and 56a in the valve block 50. Valve mechanism is therein provided for dispatching the fluid from such intermediate chambers so that the output from corresponding ones of the planet I6 may be directed either to the outlet chamber 34 or recirculated back to the intake side of the pump. lAccordingly, the volumetric output of the pump unit as a whole can be controlled by utilizing `a vdesired number of the several planets i6 to actually deliver iluid to the discharge chamber 34.

Relative to the general relation of the control valve mechanism to the impeller elements of the pump, it should be noted that although a differential type of gearing is used so that there are two series of teeth on each planet effective for pumping action, only a single valve mechanism is associated with each planet for controlling the dispatching of the fluid delivered from both of the active groups or series of teeth on such planet.

In the illustrative pump unit, valve mechanisms designated as a and b, respectively, are disposed in the two bores 55, while in each of the other three bores 55 are valve mechanisms designated as c, d and e, respectively see Fig. 9), thus affording a separate control valve for each of the iive planets I6. Of these valve mechanisms, a and b are identical in form, mechanism a being shown in detail in Fig. 4, while c, d and e are identical with each other, although somewhat different from a and b, the mechanism d being shown in detail in Fig. 3. In each case the journal pins or stub shafts I1a of the planets I6 project into the respectively opposed counterbores 56 or 56a to form part of the valve mechanisms, and have longitudinal bores l1b therein which are dead-ended at their right hand ends (as viewed in Figs. 3 and 4). Pressure fluid may be recirculated from the delivery sides of the planets back to their inlet sides through these bores I1b under the control of the corresponding valve mechanisms.

Considering rst the valve mechanism a (Fig. 4) it will be observed that it comprises as a mov.- able valve element a sleeve 59 axially slidable in the bore 55a and encircled by an integral collar 60 slidable in the counterbore 56a, such collar being adapted to abut against the shoulder at the right hand end of the counterbore to limit movement of the sleeve to the right. Movement of the sleeve to the left is limited by its abutment against the opposed portion of the wear plate I9. The sleeve 59 is telescoped over the projecting end of the pin I1 and has in it a circularly disposed series of six ports 6I, two of which are adapted to register with a pair of ports 62 in the pin I1'b when the sleeve is in its left hand position, as shown in Fig. 4. When a pair of the ports 6I are thus registered with the ports 62 pressure iiuid emitted from the pump outlet ports 38 passes through the intermediate chamber or counterbore 56B, through the registering ones of the ports 6I, 62 and thence through the bore Hb back to the pumps inlet chamber 3i. This path is shown by the line of arrows in Fig. 4. From the intake chamber pressure fluid again enters the inlet ports `31 so that its recirculation is continuous. -Upon shifting of the valve sleeve 59 to the right, however, to the position shown in Fig. 9, the ports 62 are closed, thus blocking the recirculation path through the bores 11b, and all of the six ports 6l are opened to the interior of the sleeve 59 at a point beyond the right hand end of the pin I1L so that pressure iiuid ows from the intermediate chamber 56L through the ports 6I to the outlet chamber 34. Accordingly, when the sleeve 59 is in its` right hand position, the pump element which it controls, i. e., the associatedl one of the planets I6, delivers fluid normally to the main outlet; but when the sleeve is in its left hand position it causes the delivered pressure fluid to be dispatched from such associated planet back to the intake side of the pump, thus eilectuallly cutting such planet out of service in so far as iinal delivery of iiuid from the pump unit is concerned.

As was noted above, only two ports 62 are provided in the pin I1a while a whole series, i. e., six

or more, ports 6| are provided in the sleeve 59.

intermediate chamber 56a to build up on the left` hand face oi the collar 60 asl the volume of iluid circulated increases. On the other hand, when the sleeve 59 is in its right hand position for regular delivery of fluid from the pump, the whole series of ports 6| are opened and are of suicient total cross-sectional area that there is little or no throttling caused by the ow oi.' fluid through them and hence negligible power loss-at this point. The pressure built up by the throttling caused by the restricted ports 62 is used in actuating the valve mechanism, that is to say, the

increased pressure Whichresults on the left faceA of the collar 60 is used to overpower an opposing force to shift the valve sleeve axially to the right. The opposing force is, in the present instance,

. supplied by pressure fluid admitted to the right reference to Fig. 3 it will be seen that the valve mechanism d comprises a sleeve 64 axially slidable in the bore and telescoped over the projecting end of the associated journal pin |15. This sleeve 64 has in it six ports 64 arranged to register with six ports 66 leading into the bore |11 in the pin I1, when the sleeve is in its left hand position shown.V In other words, an equal number of ports is in this case provided in both the pin and sleeve so that there is nol throttling of the fluid even during recirculation. An annular ange 61 on the outer end of the sleeve 64 slides in the counterbore 61 and Vbearing against it is a compression spring 66 whichnormally urges the sleeve to its left hand position. l

.To shift the sleeve 64 to the right, pressure iluid from a, suitable source (hereinafter described) is admitted through a port 69 to the left hand face of the flange 61. It should also be noted that the pressure of the fluid in the outlet chamber 34 actson the end face of the iiange 61 in opposition to the pressure iluid admitted through port 69 to-augment the spring 68 in urging the sleeve 64 to the left. When\the sleeve 64 is in its left hand position as shown in Fig. 3, pressure fluid delivered from the ports 38 of its associated planet I6 is recirculated back to the inlet side oi such planet through the registering ports 65, 66 and the bore I'Ib in the planets process journal pin. On the other hand, when the sleeve 64 is shifted to the right it closes the ports 66, cutting off such recirculation and establishing communication from the planet port 38 to the outlet chamber 34 to the now shifted ports 65.

From the foregoing it will be apparent that a comparatively simple valve mechanism has been incorporated in the pump unit itself and by means of which the output of the pump can be effectually controlled. For example, if the valves a, b are set for delivery while the other three valves, c, d and e, are set for recirculation, susbtantially all of the torque applied to the pump input shaft I3al is utilized in delivering iluid at a very high pressure from the two planets I6 associated with the valves a and b. The other three planets are delivering fluid against substantially no back pressure, merely recirculating it to the intake side. Then asD successive ones of the valves c, d ande are shifted from their recirculation positions to their delivery positions, the volume of pressure fluid delivered for the pump increases, although the pressure of the uid decreases. Advantage may be taken of these pump characteristics in a hydraulic transmission system such as that indicated in Figs. 1 and 9, in that the torque delivered by the fluid motor unit I2 is proportional to the pressure of the fluid supplied to it, while the speed is proportional to the volumetric rate of supply. Hence, by valving of! successive portions of the iiuid delivered from the pump unit II, the torque exerted by the motor I2 can be increased and its speed decreased, or the reverse cycle of control can be accomplished, as conditions may require. It will be perceived/that this corresponds precisely to the type of change effected in shifting gears in a. conventional gear type transmission to accommodate different torque-speed requiremen'ts.

Turning now kto a consideration of the hydraulic transmissionv system as awhole (Figs. 1 and 9) it will be seen that the pressure fluid delivered from the pump unit II passes to the motor unit I2 through the supply conduit or Pressure line 29 while the exhaust fluid from the motor unit is returned to the pump unit through the discharge or exhaust conduit 96. A reversing valve 18, of conventionalv form, is interposed in the conduits 29 and 66 so as to effect a reversal oiV the motor unit I2 when desired..

The valve 'l0 comprises a-manually operable twoposition valve element 1I having suitable peripheral grooves 12 and 13 therein which connect the conduits 29, 29" and 86, 86 when the valve element is in the'position shown and reversely assaass connect the conduits 29", 8Iil` and 36, 29* when the valve element is shifted endwise to its other:

or reversing position.

Aside from the reversing valve 1I! just described, tw'o other manually operable devices are required in the control system shown. One of these is an on-off lever 14 swingable from its "ofP position shown in Fig. 1 over to the left hand or on position shown in Fig. 9 to open a plunger valve 'I5 to start the transmission, and back to the right to close the valve and stop the For the latter -purpose a plunger 18 is arranged to unseat the valve element, this plunger being connected to a throttle pedal or lever (not shown) for the engine III so that whenever the K throttle is in its idling position the check valve 16 will be positively opened but for all other positions of the throttle the plunger I8 is disengaged from the valve element l1 so that the mechanism can function as an ordinary check valve.

To govern the operation of the transmission system automatically, under the supervisory control of the manual devices noted above, a diierential piston mechanism, designated generally as 19, is used. This mechanism I9 comprises (Fig. 9) three dierential pistons 80, 8l andiy 82 slidable in corresponding portions of a stepped cylinder 83. With the connections shown, the piston acts as a pressure multiplier in transmitting pressure from an accumulator 85 to the valve c, while the pistons 8I and 82 serve as pressure dividers in transmitting pressure from the accumulator to valves d and e respectively.

Also included in the closed hydraulic system interconnecting the pump and motor is a sump 84 and a by-passing check valve 86. This latter check valveis connected between the -pressure and return conduits 29 and 36 and serves, when open, to pass iluid from the return conduit 36 back to the pressure or supply conduit 29. The pressure at which it opens for this purpose can be adjusted byI turning a manual adjustment screw 81, the valve structure beingl of conventional form. As will appear more particularly below, this valve 86 is used to accomplish socalled free wheeling operation of the vehicle. Incidentally,` it will be assumed hereinafter, simply for purposes of description of the exemplary system, that the apparatus is used inthe drive of a vehicle such as an automobile.

In connection with the succeeding description of operation of the system, reference may be conveniently made not only to the layout of the system itself shown in Fig. 9, but also to the characteristic curves in Fig. 8. In these curves the abscissa has been graduated in increments to indicate vehicle-speed in miles per hour and also hydraulic motor speed in R. P, M., the two being, of course, directly related. 'I'he ordinate has been graduated in terms of torque, in poundfeet, on the hydraulic motor shaft and also in pressure in pounds per square inch for the pressure fluid delivered to the uid motor, these two values namely, torque-and iluid pressure, also being directly proportional. The curve designated by the legend "hydraulid indicates the operating curve for the hydraulic system herein shown. The other three curves. bearing the reassasss spective legends "first gear, "second gear and direct are typical torque-speed curves for a conventional three-speed gear-type drive for an internal combustion engine. In general, it will be observed that the curve of the present hydraulic system forms, in effect, an envelope embracing the three curves for the gear drive and thus achieves substantially the same speedtorque relation though in a smooth uninterrupted manner rather than in the steps characteristic of gear changes.

In the operation of the system, the engine I is started with the lever 14 in itsl right \hand or "oi position, thus disabling the hydraulic transmission. With the system vso conditioned, the sun gear I4 of the pump unit l2 is revolved by the engine when the latter is started, and its planets I5 all pump oil, or other suitable pressure iluid. Each of the valves a to e is in its by-passing position, however, so that no pressure fluid is delivered to the motor unit l2 but. instead, is all returned to the intake side of the pump unit. As to maintenance of the valves in closed position, it will be observed that when the lever 14 is in its oil position and the valve 15 thus closed, that uid is thereby locked in the conduit 88 (Fig. 9) so that both of the valves a and b are retained forced to the left in their by-pasing positions. The other valves c, d and e are retained in their by-passing positions by their spring loading.

With the system conditioned as described above, the lever 14 is swung to the left and the engine throttle is opened to get the vehicle under way. Such shifting of the lever 14 opens the valve 15 to unlock the pressure iuid from the outer sides of the valves a, b, connecting them instead to the sump 84,v and the opening of the engine throttle releases the plunger 18 from the check valve 16 so that the latter is free to function unhampered as a, true check valve. As the engine speed increases the rate of uid delivery from the various planets i6 for the pump unit Il increases. As heretofore noted the fluid recirculated through valves a and b is throttled by the restricted pairs of ports 52. Accordingly,

the pressure of the fluid, delivered from the planets associated with valves a and b, builds up in the intermediate chambers or counterbores 553. When the pressure in the counterbores 58" for the valves a and b reaches a predetermined point these valves are shifted. to the right (as viewed in Fig. 9) to their delivery positions shown. The point at which this shift takes place is, of course, governed by the opposing sump pressure transmitted to the outer sides of the valves through the conduit 88. Normally the sump pressure is about 100 pounds per square inch, it being supplied through a small or restricted line'84" from the main return line 88. It will thus be seen that when the p ump pressure, opposed to this sump pressure, has been built up to a suitable value the valvesa and b will be caused to shift to the right to their delivery positions so that pressure fluid issues through them to the outlet passage 34 and thence passes through the pressure conduits 29, 29* to the motor unit I2. The delivery of pressure huid to the motor unit l2 causes it to start the vehicle in motion. Since fluid is being delivered through 'only the two valves a, b of the pump unit Il the `fluid is supplied to the motor I2 at a very high pressure, building up to a peak value of, say 3,600 pounds per square inch, as shown by the hydraulic curve. in Fig. 8. This means .that maximum torque at low speed is being applied to the vehicle propeller shaft, thereby effecting a maximum rate of acceleration for the vehicle. It will be observed that the valves c, d, and e do not open contemporaneously with the valves a and b because they are spring loaded and also because there is substantially no throttling at their ports 68, as heretofore noted, and hence little build up of pressure'in their intermediate chambers or counterbores 56. Furthermore, the pressure uid delivered .through valves a and b into chamber 84 acts to augment the springs 68 in forcing the valves c, d and e to the left.

Pressure fluid at the same high pressure noted above is also delivered through a conduit 89 (Fig. 9) and the check valve 16 to the accumulator 85 and thence fbetween the opposed faces of the pistons 80, 8l. As the vehicle gains momentum the pressure in the delivery conduit 28 gradually drops, causing the check valve 16 to close with pressure fluid at the maximum or peak pressure trapped in the accumulator 85. Furthermore, the decrease in delivery pressure from the pump diminishes the pressure acting on the outer faces of the valve elements c, d and e. As this decrease continues the pressure exerted on the inner face of the valve element c,v

through the medium of the pressure-multiplier piston finally overcomes the pressure on its outer face (the latter being augmented by the spring loading) so that the latter is shifted to its delivery position shown in Fig. 9. This may occur at, for example, a pressure of 3,350 pounds per square inch. Thereupon, the three valves a, b and c deliver pressure fluid to the chamber 34 and thence to the motor unit l2. As the outlet pressure from the pump further decreases, upon further increase in the speed of the vehicle, the valves d and e are sequentially opened, through the action of the pressure applied to their inner faces through the medium of their associated pressure-divider differential pistons 8| and 82,\respectively. The valve d may, for example, be shifted to delivery position when the pump outlet pressure drops to 2,250 pounds per square inch and the final valve e shifted to delivery position when the pressure drops to 1,650 pounds per square inch. The volumetric rate of the pump is thus automatically increased progressively as the torque requirementsA of the motor diminish during vehicle acceleration. Finally, as noted, pressure iluid is delivered continuously from `all of the valves a to 'e of the pump unit ll so that the units Il and I2 are, in eiect, directly connected in a closed hydraulic system.

In the event that the torque load on the ,vehicle propeller shaft is subsequently increased, as, for example, in running up a hill,'the pressure in the delivery line 28 gradually increases. If this increase is suiilcient, the pressure on the inner face of the valve e will be overbalanced by that from the discharge chamber 34 on its outer face and this valve closed, thus correspondingly diminishing the volumetric delivery rate of the pump. Still further torque demands similarly cause all three oi' the valves e, d and c to return to their by-pass positions in the order named, so that, if necessary, the pump unit is restored to its maximum torque condition in which uid is delivered only through the valves a and b.

In the event of the opposite contingency, namely, that the vehicle is running down a hill, the unit l2 will begin to pump uid into the return line 38. 4 This builds up the pressure on a check valve 86 until it finally causes it to by-pass fluid back tothe delivery line 29 for free wheeling operation. The screw Il on the valve 8| can be adjusted to vary the pressure at which this check valve opens to by-pass fluid or, in other words, to vary the braking effect exerted by the back pressure built up on the unit l2 which is, in such case, acting as a pump. If desired a hand lever or the like (not shown) can be used to close the valve 86 in such a case and thus use the pumping action of uniti! to brake the vehicle. If it is desired to thereby brake the vehicle to a standstill the control lever 14 is swung to its of|.'" position and the valve 88 closed so that the a series of inlet ports on one side of said gearing registering with the adjacent ends of the interdental spaces of said planet gears and a series of outlet ports at the other side of said gearing registering with the opposite ends of said interdental spaces, by-pass conduits for working fluid disposed coaxially with each of said planet gears for establishing communication between its unit I2, now acting as a pump, pumps against the closed valves a to e which lock the fluid, thus stopping the unit I2 and the vehicle.

To -stop the system, the lever 1I is swung back to its o position, thereby closing the valve 'I5 and forcing uid through the conduit 88 to lock the valves o, b in their by-passing positions. When the engine throttle is dropped back to its idling position, the plunger 18l opens the check valve 18, thus releasing the pressure in the difierential piston system including the accumulator 8l. Accordingly, the whole hydraulic system is restored to its initial condition preparatory to` a subsequent cycle of operation like that described.

- To operate the vehicle in a reverse direction it is necessary simply to set the reversing valve 1D initially in its reverse position, in which the pressure conduit 29 is connected to the conduit 36* through 29 and the return conduit 3l connected to the conduit 28. In this way th e direction of huid ilow through the motor unit I2 is reversed. Otherwise, the cycle of operation is the same as that for forward operation described above. It will be noted that the same full range of torque-speed ratios is thus available for either direction of vehicle motion. 'I'his is, of course, tobe contrasted with the usual gear-type of drive inwhich only one gear ratio in reverse is commonly made available.

'I'his present application is a continuation in part of my copendins application Serial No. 356,610, :Bled September 13, 1940.

I claim as my invention:

l. In combination, a pump housing, a planetary gearing in said housing comprising a central sun gear and an encircling ring gear and a plurality of intermediate planet gears meshing with both said sun and ring gears, said housing presenting a series of inlet ports on one side of said gearing, registering with the adjacent ends of the interdental spaces of said planet gears and a series of outlet ports at the other side of said gearing registering with the opposite ends of said interdental spaces, stub shafts revoiubly supporting each of said planet gears, each of said shafts projecting laterally from the corresponding planet gears and having an axial bore therein forming a return passage from the outlet port of its planet gear to the inlet port thereof, and means including valve sleeves slidable on the projecting portions of said shafts for controlling the flow of fluid through respective ones of said return passages.

2. In combination, a pump housing, a planetary gearing in said housing comprising a central sun gear and an encircling ring gear and a plurality of intermediate planet gears meshing with both said sun and ring gears, said housing presenting outlet and inlet ports, and an individually operable shut-of! valve for each of said conduits'l 3. A pump comprising, in combination, a plurality of revoluble meshing impeller gears, a pump housing enclosing said gears and presenting an inlet and an outlet at opposite sides thereof, means forming a return passage from the outlet side of said gears to the inlet side thereof, valve means for. controlling the Adispatch of uid through said return passage and including a. twoposition valve element, said lvalve means being operable in one position of said valve element to' divert fluid-discharged from said gears into said return passage and in the other position of said valve element to block said return passage and 'dispatchiluid discharged from said gears to said outlet, said valve means also comprising means for throttling the flow of iluid therethrough substantially more when said valve element is said one position than when it is in said second fposition, and means for shifting saidvalve element from said one position to said second position in response to a predetermined maximum fluid pressure built up by said throttling action'with said valve element in said one position.

4. A pump comprising. rality of revoluble meshing impeller gears, a casing structure enclosing said gears and dening an inlet passage leading sto one side of said gears and an outlet passage on the opposite side thereof but out of direct communication with said gears,

said .casing also defining an intermediate cham- 5. A pump comprising, in combination, a plurality of revoluble meshing impeller gears, a housingstructure enclosing said gears and deflning an inlet passage on one side thereof and an outlet passage on the other side but with the latter out of direct communication with the gears, said housing also dening an intermediate chamber on said other side of said gears, a shaft coaxial with one of said gears and projecting laterally therefrom on said other side thereof, said shaft having 'a longitudinal bore therein deadended at 'the projecting end of the shaft and having a restricted port leading into it in the projecting portion of the shaft, the'opposite end of said bore leading to said inlet passage, a valve sleeve slidably telescoped over said projecting end of thev shaft and having a plurality of substantially unrestricted ports therein, said valve sleeve being shiftable endwise from a first position, in which its ports register with the shaft port to effect a throttled return flow of fluid from said in combination, a pluintermediate chamber to said inlet passage, to a secondposition in which said shaft Aport is blocked to cut off said return ow and said sleeve ports establish communication from said intermediate chamber to said outlet passage, and means operable in response to the pressure Within said. intermediate chamber for shifting said sleeve from said rst to said second position.

6. A pump comprising, in combination, a plurality of revoluble meshing impeller gears, a housing structure enclosing said gears and defining an inlet passage in one side thereof and an outlet passage in the other side but withthe latter out of direct communication with the gears, said housing also defining an intermediate chamber on said other side of said gears, a shaft coaxial with one of said gears and projecting laterally therefrom on said other side thereof, said shaft having a longitudinal bore therein leading from said inlet passage into the projecting portion of the shaft, and means including a. ported valve sleeve slidably telescoped on the projecting portion of said shaft for dispatching uid from' 'Y of spaced end structures, a drive shaft extending transversely between said structures and journaled therein, a pump gearing housed in one of said end structures and including a driving gear fixed to said shaft as well as a plurality of driven gears meshing with said driving gear, a valve housing sandwiched between the end structures, said one end structure having an inlet passage therein leading to the gearingand the other end structure having an outlet passage therein, valve means in said valve housing for controlling the dispatch to said outlet passage of uid delivered from individual ones of said driven gears, and means for ilxing said end structures and valve housing together as a unitary structure.

8. A pump comprising, in combination, a pair of spaced wear plates with a drive shaft extending transversely therethrough, a drive gear xed to said shaft and meshing with a plurality of driven gears, all of said gears being disposed between said wear plates, one of said plates having inlet ports therein and the other having outlet ports therein, an end shield overlying the outer face of said one wear plate in reenforcing relation thereto and' having an inlet passage therein leading to said inlet ports, a second end shield disposed in spaced relation to the outer face of said other plate, a valve housing sandwiched between said second end shield and said other plate in reenforcing relation with the latter, said second end shield having an outlet chamber therein, valve means within said valve housing for controllably dispatching iiuid from said outlet ports to said outlet chamber, and means securing said end shields and plates and valve housing rigidly together as a unitary structure.

9. In combination, a planetary gearing having rst and second terminal gear elements and a plurality of intermediate gear elements each meshing with both of said terminal elements. a pump casing enclosing said gearing and defining intake and delivery passages for pressure fluid to and from each of said intermediate gear elements, a plurality of valve mechanisms associated with respective ones of said intermediate gear elements and shiftable individually between delivery and return positions in which the pressure iluid from the associated intermediate gear element is respectively directed to said delivery passage and returned to said intake passage, and means operable in response to a decrease in the pressure of uid in said delivery passage from a peak value for causing said valve mechanisms to be shifted sequentially in predetermined order from their return to their delivery positions and for causing them to be restored in reverse order to their return positions in response to a subsequent increase in said pressure.

10. In combination, a planetary gearing having first and second terminal gear elements and a plurality of intermediate gear elements each meshing with both of said terminal elements, a pump casing enclosing said gearing and defining intake and delivery passages for pressure fluid to and 'from each of said intermediate gear elements, a

plurality of valve mechanisms associated with respective ones of said intermediate gear elements and shiftable individually between delivery and return positions in which the pressure fluid from the associated intermediate gear element is respectively directed to said delivery passage and returned to said `intake passage, and means for causing said valve mechanisms to be shifted sequentially in predetermined order from their return to their delivery positions and alternatively for causing them to be restored in reverse order to their return positions.

THOMAS c. PoUL'rER. 

